NILAI DIAGNOSTIK PEMERIKSAAN IMUNOSITOKIMIA LIMFOSIT SEDIAAN APUS DARAH TEPI DIBANDINGKAN ANALISIS KROMOSOM PADA PENDERITA DENGAN DUGAAN SINDROMA FRAGILE X DIAGNOSTIC VALUE OF IMMUNOCYTOCHEMICAL TEST OF LYMPHOCYTES AT PERIPHERAL BLOOD SMEAR COMPARED TO CHROMOSOMAL ANALYSIS TO DETECT FRAGILE X SYNDROME

Abstract

Background: The Fragile X syndrome is the most common heritable form of mental retardation. The diagnosis of Fragile X syndrome can be supported by chromosomal and molecular analysis. Fragile X Mental retardation Protein (FMRP) is a protein that involved in mRNA metabolism and found in several tissues with predominant location in cytoplasm. Immunocytochemical study can detect the presence of FMRP in cytoplasm of lymphocytes. Objective: To investigate the sensitivity, specificity, positive and negative predictive value, and likelihood ratio of immunocytochemical test of lymphocytes at peripheral blood smear compared to chromosomal analysis. Material and method : Twenty consecutive samples were obtained from students of special school (SLB) at Semin Gunung Kidul. The inclusions criteria were male >7 years old, mild to moderate mental retardation, no Down syndrome, no multiple malformation, and no dumbness and deafness. Heparinized peripheral blood samples were cultured in low folate TC 199 and MEM + thymidine media to analyze the expression of fragile sites. The presence of FMRP protein in lymphocyte was analyzed by immunocytochemical techniques using monoclonal antibody against FMRP. Result of immunocytochemical test for detecting FMRP expression from lymphocyte in blood smear was tabulated and compared to chromosomal analysis that used as the gold standard. Then, the data was summarized into table 2 x 2 and calculated for sensitivity, specificity, positive and negative predictive values, and likelihood ratio. Result : The sensitivity, specificity, positive predictive value, negative predictive value of immunocytochemical test were 93,33%, 40%, 83,25% and 66,66% respectively. The positive likelihood ratio of immunocytochemical test was 1,55 and the negative likelihood ratio of immunocytochemical test was 0,16 Conclusion : Immunocytochemical test had high value in the sensitivity and positive predictive value but had poor value in specificity, negative predictive value and positive likelihood ratio. Immunocytochemical test of lymphocytes at peripheral blood smear can be used for patients screening of the Fragile X syndrome. Latar belakang : Sindroma Fragile X merupakan penyebab utama retardasi mental. Diagnosis Fragile X dapat ditegakkan dengan analisis kromosom dan molekuler. Fragile X Mental Retardation Protein (protein FMRP) adalah molekul yang berperan dalam metabolisme mRNA. Protein ini terletak di sitoplasma dan terekspresikan secara luas pada banyak sel. Pemeriksaan imunositokimia dapat mendeteksi adanya protein FMRP di sitoplasma limfosit. Tujuan : Untuk mengetahui sensitivitas, spesifisitas, nilai ramal positif dan negatif, serta rasio likelihood dari tes imunositokimia limfosit pada sediaan apus darah tepi (SADT). Bahan dan metoda : Sebanyak 20 sampel diambil secara konsekutif dari siswa SLB di Semin Gunung Kidul. Kriteria inklusi adalah siswa pria berumur > 7 tahun, penderita retardasi mental ringan sampai sedang, bukan penderita sindroma Down, tidak menderita malformasi multipel, dan bukan penderita bisu tuli. Darah vena berheparin dikultur di media rendah folat TC 199 dan MEM + thymidine untuk melihat ekspresi fragile site. Protein FMRP di sitoplasma limfosit diperiksa dengan imunositokimia menggunakan antbodi monoklonal terhadap FMRP. Hasil pemeriksaan protein FMRP limfosit pada SADT dibandingkan dengan analisis kromosom yang digunakan sabagai baku emas. Selanjutnya data dimasukkan dalam tabel 2 x 2 dan dihitung sensitivitas, spesifisitas, nilai ramal positif dan negatif, serta rasio likelihood. Hasil : Pemeriksaan imunositokimia limfosit di SADT mempunyai sensitivitas 93,33%, spesifisitas 40%, nilai ramal positif 83,25% dan nilai ramal negatif 66,66%. dalam mendeteksi sindroma Fragile X. Rasio likelihood positif dari pemeriksaan imunositokimia adalah 1,55 sedangkan rasio likelihood negatifnya adalah 0,16 Simpulan : Pemeriksaan imunositokimia limfosit di SADT mempunyai sensitivitas dan nilai ramal positif tinggi, namun mempunyai spesifisitas, nilai ramal negatif dan rasio likelihood positif yang rendah. Pemeriksaan imunositokimia limfosit di SADT dapat digunakan untuk uji saring penderita sindroma Fragile X.